1. Field of the Invention
The present invention relates to a removable data storage cartridge and to a data storage drive for receiving same. More particularly, the present invention relates to methods and apparatus for detecting the presence of the correct disk cartridge in the data storage drive, and to protecting against the insertion of incompatible or write protected disk cartridges in the drive.
2. Description of the Prior Art
Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses a rotatable recording medium, or disk, upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk. The disk is mounted on a hub that rotates freely within the cartridge. When the cartridge is inserted into a disk drive, a spindle motor in the drive engages with the disk hub in order to rotate the disk within the cartridge. The outer shell of the cartridge typically has some form of opening near its forward edge to provide the recording heads of the drive with access to the recording surfaces of the disk. A shutter or door mechanism is often provided to cover the opening when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.
Disk drives for receiving removable disk cartridges, including conventional 3.5" floppy disk drives, must have some mechanism for detecting the insertion or presence of a disk cartridge in the drive. The actuator that carries the recording heads of the disk drive across the recording surfaces of the disk should not be allowed to move unless the presence of a disk cartridge is detected. In the prior art, mechanical switches are typically employed to detect the presence of a disk cartridge within the drive. Such switches are typically positioned such that when a disk cartridge is inserted fully into the drive, the cartridge contacts the switch, thereby providing an indication that the disk cartridge is present.
When a data storage cartridge is inserted into a drive it is important that the type of cartridge be recognized by the drive as the correct type for safe and reliable use in that particular drive. Most removable cartridge drives (magnetic and optical) typically use approximately the same form factor cartridges, i.e., 3.5", 5.25", etc. Hence if one of these cartridges is inserted into the cartridge slot of the non-mating drive there is a large probability that either the drive (heads, load mechanism, electronics, etc.) or the data on the disk could be damaged.
Also, some cartridges are "write protected" by the user to prevent accidential erasure of important data by writing over it. It is important to protect against operation of the drive when an incorrect or write protected cartridge is inserted.
Recently, retroflective materials have been developed. This material has many periodic miniature corner cubes, or spherical elements, which reflect light striking it almost exactly upon its incident path. Retroflective array materials are described in Jacobs, S. F., "Experiments with retrodirective arrays," Optical Engineering, Vol. 21, No. 2, March/April 1982; Rennilson, J., "Retroreflection--What is it and how is it used? " ASTM Standardization News, Feb. 1982; and Venable, W. H., Stephenson, H. F. and Tersteiege, H., "Factor affecting the metrology of retroflective materials," Applied Optics, Vol. 19, No. 8, Apr. 15, 1980.
It is an object of the present invention to provide a retroreflective marker on a data storage cartridge in order to prevent damage to the drive or the storage medium by insertion and attempted writing/reading of an improper cartridge, or writing on a "write protected" cartridge.